Multicontrast photographic emulsions



July 12, 1960 Filed Jan. 18, 1957 Fi g1 DENSITY DENSITY B. H. CARROLL MULTICONTRAST PHOTOGRAPHIC EMULSIONS 2 Sheets-Sheet 1 L 06 EXPOSURE v.0 L38 2b LOG EXPOSURE Burl II. Carroll INVEN TOR.

AT TORNEYS July 12, 1960 B. H. CARROLL MULTICONTRAST PHOTOGRAPHIC EMULSIONS 2 Sheets-Sheet 2 Filed Jan. 18, 1957 i0 L3 8 25:) 2'38 L O G EXPOSURE 0 o 6 2 O 8 6 A 2 0 158 2'0 LO (5 EXPOSURE m ZwwHRLBB Z .BurtHO'arroll IN V EN TOR.

ATTORNEI'TS ice 7 Fa -measure l2, rseo nearly all of the available light-absorbing materials have an adverse effect upon the emulsion and especially on 2,944,901, the optical or spectral sensitizing dyes customarily em- MULTICONTRAST PHOTOGRAPHIC EMULSIONS Burt H. Carroll, Rochester, N.Y., assignor to Eastman Kodak'Company, Rochester, N.Y., a corporation of New Jersey Filed Jan. 18, 1957, Ser. No. 634,944

4 Claims. (Cl. 96-102) Photographic silver halide, emulsions intended primarily for themanufacture of printing materials having various degreesf'of contrast under the same conditions of development have been preparedin the past by coating in layers, or mixing together, two different silver halide emulsions having diiferent contrasts (gamma). Thus, for example,

an emulsion which has high contrast and is sensitive to blue, such as a silver chlorideemulsion, can be mixed with an emulsion whichhas low contrast and is sensitive to green, such as a spectrally sensitized silver bromide emulsion. If such .afcomposite emulsion is exposed to light passing through a blue-green filter, the emulsion works normally and is suitable for negatives of normal gradation or contrast. if, however, it is desired to print from a negative with a wide range of densities, the light which acts upon'the high-contrast emulsion is cut off by means of a filter permeable only to green, and a normal picture is obtained by means of the low-contrast emulsion. n the other hand, if it is desired to print name negative with but little contrast, the light which acts upon the low contrast emulsion is cut olf by means of a filter permeable only to blue and a normal picture is obtained by means of the high-contrast emulsion.

One of the major problems in multicontrast materials, however, is to secure a suitable balance of sensitivities and density scales in the two emulsions so that it is possible to print a range of contrasts between the two extreme values of contrast. ,If the sensitivities and scales of the two components through the appropriate filters are not equal, attempts to print intermediate contrasts by a mixture of green and blue light will result in badly distorted characteristic curves and very poor tone reproduction. I V

The above method for making photographic prints which vary in contrast has not been found useful in the preparation of multicontrast emulsions of long scale which will reproduce negatives of great density range in the form of prints to be viewed by transmission. Furthermore, whenmixtures of emulsions of different composition and development rates are used, the results are sensitive to development conditions,

One of-the methods proposed for making multicontrast emulsions which are useful in the manufacture of transparencies is to add to the emulsion a material absorbing a region of the spectrum to which the emulsion is sensitive, in suliicient quantity so'that the contrast for that region is lowered. This insuresthat the scale ofthe emulsion-for this region will be lengthened, since the contrast is lowered without any loss of maximum density. It also provides a material which in its normal contrast range can be used for printing average negatives. In the region containing the absorber, negatives of high contrast and wide density range can beusedfto produce normal prints. However, such materials containing a light-absorbing dye are quite diflicult to produce since which is the 'minimum requirement for most multicontrast applications, inevitably causes a decrease in sensitivity to the region adsorbed by a factor of about ten from the absorption alone." Unless the absorber is except'ionally free from desensitizing effects, there will be serious loss of sensitivity for all regions of the spectrum, and the sensitivity in the region of low contrast will be so' low that it is impossible to balance sensitivities. It has also been found diificult to select absorbing materials which act as selectively as desired. 'The absorption bands of many dyes are so broad that the addition of a sufficient quantity to the emulsion to lower the contrast in the green causes a serious loss of speed in the blue region because the dye also absorbs blue. Furthermore, many of thelight-absorbing dyesus'ed in photography fail to bleach or washout completely in processing. The sensitizing dye used must give very selective absorption for the region covered by the light-absorbing dye, since a small extension of sensitivity past the region of heavy absorption will give an unsatisfactory curve shape for the characteristic curve, with a toe of the desired contrast and a high contrast shoulder. In'addition, the sensitizing; dye must function satisfactorily in the'presence of the light-absorbing dye. a i

It is, therefore, an object of my invention to provide: photographic silver halide emulsions showing varying;

degrees of contrast, depending upon the spectral distribu tion of the exposing source. Another object of my inven-- tion is to provide photographic silver halide emulsions; showing varying degrees of contrast which are particularly useful in the manufacture of prints which are to be viewed by transmission. Still another object is to pro-- vide a method for making such photographic silver halide emulsions. Other objects will become apparent from a consideration of the following description and examples.

According to my invention, I provide photographic silver halide emulsions showing varyingdegrees of contrast by incorporating therein a light-absorbing oxonoI dye containing a 3-methyl-l-sulfophenyl-S-pyrazolinone nucleus or .a barbituric acid (but not thiobarbituric acid)- nucleus, and a spectral sensitizing dye selected from the group consisting of (1) a cyanine dye containing a 5- phenylbenz othiazole nucleus, (2) a cyanine dye containing at least one carboxyalkyl group, (3) a cyanine dyecontaining at least one sulfoalkyl group, (4) a merocyanine dye containing a carboxyl group, (5) a merocyanine dye containing a sulfo group, and (6) 4-[(l,3,3- trimethyl 2 (3H) indolylidene)ethylidene] 3 methyl-l-phenyl-5-pyrazolinone. While a very high proportion of sensitizing dyes fail to sensitize satisfactorily inthe presence of such oxonol dyes, the dyes enumerated above have been found to be quite satisfactory in providing multicontrast materials according to my invention. For the purposes of my invention, the above-enumerated sensitizing dyes should have their maximum absorption in the same region of the spectrum as the -oxonol dyes,-

by the following:

* .(2) 3,3 diethyl 5,5',9 tripheriylthiacarbocyanine p' toluenesulfonate;

3 f 3) 3 ethyl- 3' methyl 5,5',9 -tri1:|henylthiacarbocyanine p toluenesulfonate. (4) 3,3,9 triethyl 5,5 diphenylthiacarbocyanine iodide. Group B. Carboxyalkyl cyanine dyes:

(1) Anhydro 3 p carboxyethyl 1' ethylthia 2' cyanine hydroxide. (2) Anhydro 1 carboxymethyl 3 ethylthia 2' cyanine hydroxide. (3) Anhydro 3,3 dicarboxymethylthiacyanine hydroxide. 4) Anhydro 3 carboxymethyl 1' ethylthia 2' carbocyanine hydroxide. (5) Anhydro 3,1 di e a carboxyethylthia 2' cyanine hydroxide. Group C. Sulfoalkyl cyanine dyes:

(1) Anhydro 1,5 chloro 3. ethyl 3' 5 sulfoethylthiacyanine hydroxide; (2). Anhydro 1 ethyl 3 e sulfoethylthia 2" cyanine hydroxide. (3) Anhydro 3 J3 -'carboxyethyl 5,5 dichloro 9 ethyl 3' 18 sulfoethylthiacarbocyanine hydroxide. (4) Anhydro 5,5 dichloro 9 methyl 3,3 di

B sulfoethylthiacarbocyanine hydroxide. Group D. Carboxy-merocyanine dyes:

, 4 drogen atom, an alkyl group (e.g., methyl, ethyl, etc.), or an aryl group (e.g., phenyl, tolyl, etc., especially a mononuclear aryl group of the benzene series containing from 6 to 7 carbon atoms), n represents a positive integer of from 1 to 2, X represents an acid radical, such as chloride, bromide, iodide, p-toluenesulfonate, benzenesulfonate, methylsulfate, ethylsulfate, perchlorate, etc., and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the type customarily employed in (1) 3 (p carboxyphenyl) 5 [(3 ethyl-26H) benzothiazolylidene) ethylidene] rhodanine.

(2) 5 (1 n butyl 4(1H) quinolylidene) 3 carboxymethylrhodanine.

(3) 3 carboxymethyl 5 [(3 methyl 2(3H) thiazolinylidene)ethylidene] 2 thio 2,4 oxazolidinedione.

(4) 4 [(3 ethyl 2(31-1) benzothiazoly1idene)- isopropylidene] 3 methyl 1 p carboxyphenyl 5 pyrazolinone.

Group E. Sulfo-merocyanine dyes:

(:1) 4 3 ethyl 2(3H) benzothiazolylidene)- isopropylidene] 3 methyl 1 p sulfophenyl 5 pyrazolinone.

(2) 5 [(3 methyl 2(3H) benzoxazolylidene):

ethylidene] 3 B sulfoethylrhodanine.

(3) 4 [(3 ethyl 5 phenyl 2(3H) benzoxazolylidene)ethylidene] 3 methyl l psulfophenyl) 5 pyrazolinone.

(4) 5 [(3 methyl 2(3H) thiazolinylidene)isopropylidene] 3 B sulfoethylrhodanine.

' The light-absorbing oxonol dyes which have been found to be useful in my invention can be illustrated by the following:

Oxonol dyes:

(1) Bisll (p sulfophenyl) 3 methyl 5 pyrazef linone] trimethineoxonol.

(2) BisEl (p -tsulfophenyl) 3 methyl 5 pyrazolinone]pentamethineoxonol.

(3) Bis[l,3 :diethylbarbituric acid (5)]pentamethineoxonol.

(4) 1 methyl 1 [1 (p suliophenyl) 3 methyl 5 pyrazolinone] 3 [1 phenyl 3 methyl 5 pyrazolinone]trimcthineoxonol.

(5) 1,3 diethylbarbituric acid (5)][3 methyl l phenyl 5 pyrazolinone]trimethineoxonol.

The 5-phenylbenzothiazole dyes [useful in practicing my inventioncan be represented by the following general formula:

wherein R and R each represents an alkyl group, such as methyl, ethyl, p-hydroxyethyl, etc. (e.g., 1 an alkyl group containing from 1 to Zcarbonatoms) Rgreprescnts a hythe cyanine dye art, such as those of the benzothiazole series, those of the benzoxazole series, thoseof the benzoselenazole series, those of the naphthothiazole series, those of the quinoline series, etc. Dyes of the type represented 'by Formula I above can advantageously be prepared according to methods already described in the prior art, such as in U.S. Patent 2,763,646, issued September 18, 1956.

The cyanine dyes containing a carboxyalkyl or a sulfoalkyl group useful in my invention can be represented by the following general formula: j

ample, those nuclei listed above forVZ. The dyes repre-;

sented by Formula 11 above can advantageously be pre-. pared as described in US. Patents 2,213,995; 2,231,658; 2,238,231; and 2,503,776.

The merocyanine dyes containing a carboxy or sulfo group useful in practicing my invention comprise the dyes represented by the following general formula:

Q\\ R-I-i -oH-=e11),,-1- b(=L-L)q 1; e=o wherein R, n and Z each have the values given above, q represents positive integer of from 1 to'3,'L represents a methine group (i.e., a -CR= group whereinfR' represents a hydrogen atom or an alkyl group, such as methyl, ethyl, etc.), and Q represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the type customarily employed in the merocyanine dye art, such as rhodanine, pyrazolinone, Z-thiohydantoin, 2-thio-2,4-oxazolidinedione, etc. The dyes represented by FormulaIII above can be prepared according tothe method shown in US. Patents 2,493,747 and 2,493,748.

The dyes represented by Formulas I, II and III above wherein Z and/or'Z represent a heterocyclic nucleus containing a fused-on benzene ring can have simple suband 2,621,125. The effect obtained with the mixtures of light-absorbing dyes and spectral sensitizing dyes according to my invention varies depending upon the quantity of light-absorbing dyes present, the ratio of sensitizing dye to light-absorbing dye, the particular silver halide emulsion, etc. The most useful combinations can be ascertained by simply preparing a series of test coatings varying the ratio of the sensitizing dye to absorbing dye in a particular emulsion. The quantity of a given dye will vary depending upon thepurpose for which the emulsion is to be employed. [In general, a sufiicient quantity of absorbing dye should be-employed so that the photographic silver halide emulsionhasl a contrast'in its unsensitized region at leasttwice that for the sensitized region. Obviously, the exact amounts will vary depending upon the p ayedone carboxyalkyl group is employed in combination with a light-absorbing dye of the oxonol dye series containing a 3-methyl-1-sulfophenyl-5-pyrazolinone nucleus, although the results have not been as outstanding as in the case of the indolenine merocyanine dye mentioned above. It can be seen by reference to Fig. 4 of the accompanying drawings that this particular merocyanine dye has given quite outstanding results.

The following examples will serve to illustrate more fully the manner of practicing my invention.

Example 1 A high contrast gelatino-silver-chlorobromide emulsion was sensitized with 3,3'-dimethyl-5,5',9-triphenylthiacarbocyanine bromide (154 rug/mole AgX) giving the emulsion a sensitizing maximum at 630 mu. To portions of this emulsion were added varying amounts of the absorbing dye, bis[3-methyl-l-(p-sulfophenyl)-5-pyrazolinone] 'pentamethine oxonol.

The sensitivity of the emulsion to red light, transmitted by a Wratten No. 25 filter (i.e., a filter transmitting radiation only beyond about 585 mu) was measured by exposure in an intensity scale sensitometer. The sensitivity to blue light, transmitted by a Wratten No. 47 filter (i.e., a filter transmitting only between about 370 and 515 mu) was measured at the same time. Development was for 4 minutes in Kodak Developer D-19. The quantity of light-absorbing dye used is given in the following table, together with the speed and gamma for the resulting coatings. The sensitivity or speed is expressed by the formula l(ll og E) where E is the exposure in meter candle seconds of radiation from an incandescent light source of 3000 K. incident on the filter required to produce a density of 0.3 above fog.

Since the gamma values of the above table do not satisfactorily express the effective contrast produced by the coatings, the accompanying drawings illustrate the characteristic curves for these coatings. These characteristic curves are discussed in detail below. The particular light-absorbing dye employed in Example 1 has its maximum absorption at about 640 mu, with very little absorption below about 550 mu.

Example 2 A high contrast gelatino-siIver-chlorobromide emulsion Was sensitized by adding 150 mg./mole AgX of 4-[(1,3,3- trimethyl 2( 3H) indolylidene)ethylidenel 3 methyll-phenyl-S-pyrazolinone from acetone solution. Then 7.0 g./mole of AgX of bis[Ii-methyl-l-(p-sulfophenyl)-5- pyrazolinonel trimethine oxonol was added in neutralized aqueous solution, and the emulsion was coated in the usual manner at 250 square feet per mole of silver halide. The sensitivity of the coatings to green light was measured by exposure in an intensity scale sensitometer through a Wratten No. 12 filter (i.e., a filter transmitting only light beyond 495 mu), while the sensitivity to violet light was measured by exposure through aWratten No. 35 filter (i.e., a filter transmitting light between about 320 470 mu and beyond 660 mu). Development was for four minutes in a developer (Kodak D-19) having the following composition:

Water, about F -cc 500 Nmethyl-p-aminophenol sulfate g 2.0 Sodium sulfite (desiccated) g 90.0 Hydroquinone g 8.0 Sodium carbonate monohydrate g 52.5 Potassium bromide g 5.0

Cold water to make one liter.

After fixing, washing and drying, the characteristic curves of the coatings were prepared as in Example 1. The gamma of the film exposed through the No. 12 filter was 1.05, while that for the coating through the No. 35 filter was 2.25. These characteristic curves are shown in the drawings, which are discussed below.

Example 3 Results similar to those of Example 2 were obtained by replacing the sensitizing dyeof that example with g. of S-fl-carboxyethyl-l'-ethylthia-2-cyanine iodide.

While the above examples have been particularly concerned with the use of silver chlorobromide emulsions because of their freedom from sensitivity in the bluegreen region, it is to be understood that my invention can also be employed with other photographic silver halide emulsions, such as gelatino-silver-chloride, -bromide, -chlorobromiodide, ebromiodide, etc.

The ratio of the various silver halides in the elements of varying contrasts can also be varied depending upon the degree of contrast desired, speed desired, etc.

The emulsions can also be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added, such as those described in Sheppard U.S. Patent 1,574,944 and U.S. 1,623,499, and Sheppard and Brigham U.S. Patent 2,410,689.

The emulsions can also be treated with salts of the noble metals, such as ruthenium, rhodium, palladium, iridium and platinum, all of which belong to group VIII of the periodic table of elements and have an atomic weight greater than 100. Representative compounds are ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as describedin Smith and Trivelli U.S. Patent 2,448,060, and as anti-foggants in higher amounts, as described in Trivelli and Smith U.S. Patents 2,566,245 and 2,566,263.

The emulsions can also be chemically sensitized with gold salts as described in Waller and Dodd U.S. Patent 2,399,083, or stabilized with gold salts as described in Damschroder U.S. Patent 2,597,856 and Yutzy and Leermakers U.S. Patent 2,597,915. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agents, such as stannous salts (Carroll U.S. Patent 2,487,850), polyamines, such as diethylene triamine (Lowe and Jones U.S. Patent 2,518,698), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925), or bis-(,S-aminoethyl) sulfide and its watersoluble salts (Lowe and Jones U.S. Patent 2,521,926).

The emulsions can also be stabilized with the mercury compounds of Allen, Byers and Murray U.S. Patent 2,728,663, Carroll and Murray U.S. Patent 2,728,664, and Leubner and Murray U.S. Patent 2,728,665.

The amounts of light-absorbing dyes used in the multicontrast emulsions of my invention can be varied, depending upon the degree of contrast desired in the sensitized region. In general, I have found that from about 4 to 25 g./mole of silver halide of the light-absorbing dyes can be employed. The amounts of sensitizing dyes used can also be varied, depending upon the elfects desired, In general, from about to about 300 rug/mole of silver halide of the sensitizing dyes can be employed. The ratio of light-absorbing dye to sensitizing dye can likewise be varied, although suflicient light-absorbing dye should be employed to give a contrast in the unsensitized region at least twice that for the sensitized region.

The accompanying drawings will serve to illustrate further the results obtained in my invention. Each figure in the drawings is a diagrammatic reproduction of the characteristic curves of the emulsions described in Examples 1 and 2 above. Figure 1 is a diagrammatic reproduction of the characteristic curves obtained from coating (a) of Example 1. Curve B of Fig. 1 represents the characteristic curve of the emulsion exposed With the Wratten No. 47 filter, i.e., to blue light. Curve A of Fig. 1 represents the characteristic curve of theemulsion exposed using the Wratten No. 25 filter, i.e., exposure to red light.

In Fig. 2, curve C represents the characteristic curve of the emulsion of coating (b) of Example 1 exposed using the Wratten No. 47 filter, i.e., exposure to blue light, whilecurve'D represents the characteristic curve of the same emulsion exposed using the Wratten No. 25 filter, i.e., exposure to red light.

In Fig. 3, curve F represents the characteristic curve Of'fllfi emulsion of coating (c) of Example 1 exposed using a Wratten No. 25 filter, i.e., exposure to red light, while curve B represents the characteristic 0 rve of the emulsion of coating (0) of Example 1 exposed using a Wratten No. 47 filter, i.e., expo-sure to blue light.

It can readily be seen by comparison of the characteristic curves of Figs. 1, 2 and 3 that the curves give a more accurate evaluation of the characteristics of the multicontrast emulsions than the gamma figures set forth in'Example l.

In Fig. 4, curve G represents the characteristic curve of the emulsion of Example 2 exposed using a Wratten No. 35 filter, i.e., exposure to violet light, while curve H represents thecharacteristic curve of the same emulsion exposed using a Wratten No. 12 filter, i.e., exposure to green light. The long scale of the curve obtained by exposure to green light is quite apparent, and it can be secnthat the sensitivities through the two filters are quite similar, so that it is easy-to adjust exposures to give any required gamma between these two limits. In addition, in this type of film using a single emulsion, the relative contrastsare almost independent of processing conditions. I a

It can be seen from the characteristic curves shown in the drawings that my invention can be used when the emulsion has been sensitized either for the green or red regions of the spectrum. Since most emulsions have an inherent sensitivity lying in the blue region of the spectrum, it is obvious that the sensitizing dye employed should generally have its maximum sensitization beyond the blue region of the spectrum. The combination illustrated in Example 2 above has been found particularly outstanding in that an exceptionally wide range of exposures and varying contrasts is provided.

As shown in the above examples, the oxonol dyes can be added to the emulsions in the form of their neutral aqueous solutions. Thus, the acidic dyes are at least partially neutralized. Neutralization can be effected by the usual alkaline or basic agents, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, triethylamine, pyridine, etc. It is to be understood that the term oxonol dye as used in the fore going specification and claims includes either the acid or base form of the dye. Also, the term sulfo as used inltheforegoing specification isintended to include not only the -SO H group but the salt forms of this group While the term -a barbituric acid nucleus" is generally understood in .the sensitizing dye art to include Z-thiobarbituric.,;ac id, it is not so definedin the present invention since'dyes derived .from 2-thiobarlbituric acid 3 show an undesirable desensitizing action. The foregoing description and claimsshould be interpreted accordingly. As indicated above, the alkyl group' represented by R can be a substituted alkyl group, such as fi-hydroxyethyl,

, carboxymethyl, fl-carboxyethyl, sulfomethyl, B-sulfoethyl,

etc. With respect to the dyes represented by Formula 11 above, those dyes wherein R is a sulfoalkyl or carboxyalkyl group have been found to provide quite useful results. 4 l,3,3-trimethyl-2( 3H) -indolylidene)ethylidene] -3-methyl l phenyl 5 pyrazolinone has been found to be among the most useful of all sensitizing dyes employed inmy invention.

What I claim as my invention and desire secured by Letters Patent of the United States:

1. A photographic silver halide emulsion sensitized with a spectral sensitizing dye selected from the group consisting of (1) an acid merocyanine dye selected from those represented by the following general formula;

to 2 carbon atoms, L represents a TCR group, wherein' R represents a member selected from the group conteger of from 1 to 2, q represents a positive integer of from lqto 3, Z representsthe non-metallic atoms necessary-to complete a heterocyclic nucleus selected from the group consisting of those of the benzothiazole series, those of benzoxazole series, those of the benzoselenazole series, those of the naphthothiazole series, and those of the quinoline series, and Q represents the non-metallic atoms necessary to complete a heterocyclic nucleus selected from the group consisting of those of the rhodanine series, those of the pyrazolinone series, those of the 2- thiohydantoin series, and those of the 2-thio-2,4-oxazolidinedione series, said heterocyclic nucleus defined by Q containing an acid group selected from the group consisting of carboxyalkyl, sulfoalkyl, carboxyaryl and sulfoaryl, said acid group being attached to the nitrogen atom of a heterocyclic ring of said merocyanine dye, and (2) 4 1,3,3 trimethyl 2(3H)-indolylidene)ethylidenel-3- methyl-l-phenyl-S-pyrazolinone, the amount of said sensitizing dye beingfrom about 5 to 300 mg./mole of silver halide, said silver halide emulsion containing from about 4 to 25 g./mole, based on the amount of silver halide, of a light-absorbing oxonol dye selected from the class consisting of a trimethine oxonol dye and a pentamethine oxonol dye, said oxonol dye having -a 3-met-hyl-l-(sulfophenyl)-5-pyrazolinone nucleus attached to one end of the methine chain through the 4-position of said 3 meth yl-l-(sulfophenyl)-5 pyrazolinone nucleus, and attached to the other end of said methine chain a-second nucleus selected from the class consisting of a 5-pyra zolinone nucleus and a 2,4,6rtriketohexahydropyrimidine nucleus, said second nucleus being attached to said methine chain through the methylene group of said second nucleus, and said light-absorbing oxonol dye having its maximum absorption in substantially the same region of the spectrum as said sensitizing dye, the amounts of said sensitizing dye and said light-absorbing'dye being such that said emulsion has a contrast for the unsensitized region of the spectrum at least twice that of the sensitized region, said sensitized dye having its maximum absorption beyond about 480 m l.

linone and containing from about 4 to 25 g./mole, based on the silver chlorobromide, 'of a light-absorbing oxonol dye selected from the class consisting of a trimethine oxonol dye and a pentamethineoxonol dye, said oxonol dye having a 3'methyl-1-(sulfophenyl)-5-pyrazolinone nucleus attached to one end of the methine chain through the 4-position of said 3-methyl-l-(sulfophenyl)-5-pyrazolinone nucleus and attached to the other end of said methine chain a second nucleus selected from the class consisting of a 5-pyrazo1inone nucleus and a 2,4,6-t-riketohexahydropyrimidine nucleus, said second nucleus 'being attached to said methine chain through the methylene group of said second nucleus, said light-absorbing oxonol dye having its maximum absorption in substantially the same region of the spectrum as said sensitizing dye, the amounts of said sensitizing dye and said light-absorbing dye being such that said emulsion has a contrast for the unsensitized region at least twice that for the sensitized region.

4. A photographic silver chlorobromide emulsion sensitized with from about 5 to 300 mg./mole, based on the silver chlorobromide, of 4-[(1,3,3-trimethyl-2(3H)- indolenylidene ethylidene] -3- methyl-1-phenyl-5-pyrazo- References Cited in the file of this patent UNITED STATES PATENTS 2,493,747 Brooker et a1. Jan. 10, 1950 2,533,472 Keys et a1. Dec. 12, 1950 2,588,615 Capstafi Mar. 11, 1952 2,611,698 Jenner Sept. 23, 1952 FOREIGN PATENTS 700,734 Great Britain Dec. 9, 1953 OTHER REFERENCES Capstafi et al.: Transactions of the Society of Motion Picture Engineers, X, pp. 223-229, February 1927.

Patent should read as corrected below.

column 8 line 73,- for 'indoyli dene) f read me indolylidenel column 9,, line 21 for "indolenylidene'" read em indolyli= dene) n, i

UNITED STATES PATENT OFFICE CERTIFICATE OF COBECTION Patent No,. 2 944 9Ol July 12 1960 Burt H, Carroll It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Column 3 line 41 for "(S lmatlhyl read (S eLhyl Signed and sealed this 3rd day of January 1961s (SEAL) Attest:

KARL H. AXLINE ROBERT c. WATSGIN Attesting Ofiicer a Commissioner of Patents 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION SENSITIZED WITH A SPECTRAL SENSITIZING DYE SELECTED FROM THE GROUP CONSISTING OF (1) AN ACID MEROCYANINE DYE SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA: 